Is most prevalent in water and undercooked meats, but can be carried in any foodstuff

A 1996 outbreak in Japan affected about 10,000 people

Cambridge-based Acambis wants to test a genetically modified form of E. coli, the food- and water-borne bacterium that causes some 40% of incidences of diarrhoea.

A government advisory committee is deciding on Thursday whether to approve clinical trials - a necessary step since they would involve the release of genetically modified organisms (GMOs) into the environment.

If, as seems likely, the committee gives the go-ahead, trials will take place this summer at a London hospital.

But it will still be 2008 before the vaccine becomes commercially available - if trials are successful, which is far from certain.

Tummy trouble

Despite a number of previous attempts, no firm has yet successfully developed an effective vaccine against diarrhoea.

Acambis' product will attack enterotoxigenic E. coli, which causes gastroenteritis and diarrhoea, mainly in travellers and infants in countries with poor sanitation.

E. coli causes two-fifths of diarrhoea worldwide

If universally distributed, the jab could save the lives of 500,000 children a year in the developing world, Acambis claims.

The company also foresees that it could be available as a pre-holiday jab for holidaymakers, possibly topped up once a year.

Surveys suggest that some 50% of Britons travelling abroad suffer from stomach upsets of some sort.

Sensitive issue

The fact that the Acambis product is genetically modified has made it mildly controversial, however.

Genetic modification in production of medicines has so far attracted far less popular opposition than its use in food.

But because the planned trials will involve live GMOs getting into the British sewerage system, they have to be approved by the government's Advisory Committee on Releases to the Environment (Acre).

Acre has considered Acambis' application twice this year already, and has expressed reservations on the safeguards it has set in place.

According to Whitehall sources, controversy over GM foods and the MMR vaccine has made the government twitchy about waving through new projects without thorough investigation.

Beware biotech boasting

Experts also caution against premature excitement.

Any vaccine against E.coli may well be useful as a holiday jab, but may be less useful in eliminating the scourge of diarrhoea in poor countries.

Diarrhoea is the biggest killer of children in the developing world, but the main cause is a bug called rotavirus, and cost considerations may make universal distribution impracticable in any case.

There is also a long history of biotech firms researching drugs that never come to market - something that causes their share prices to see-saw wildly.

Acambis has a strong track-record, however, having developed successful vaccines against diseases including smallpox and yellow fever.